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      <title>目前准备做数据库水平切分，需要注意什么关键问题？ - 交互式测验</title>
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    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>目前准备做数据库水平切分，需要注意什么关键问题？ - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
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                    <div class="progress-bar">
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  {
    "question": "根据文档，选择分片键（Sharding Key）时，首要的核心考虑因素是什么？",
    "options": [
      "分片键的数据类型必须是整数类型",
      "应基于业务需求，确保大多数查询能在单个分片内完成",
      "必须使用数据库表的主键作为分片键",
      "选择更新最频繁的字段以提高写入性能"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档强调，分片键应基于业务需求选择，其核心目标是让大多数查询能够局限在单个分片上完成，从而减少跨分片查询带来的复杂性和性能开销。同时，分片键还应能均匀分布数据，避免数据热点。",
    "source": "文档中「1. 分片策略选择」-「分片键选择」部分",
    "hint": "思考一下，分库分表的初衷之一是为了提升查询效率，那么选择分片键时应该如何服务于这个目标？"
  },
  {
    "question": "在分库分表后，当一个业务操作（如创建订单和扣减库存）需要同时修改多个分片上的数据时，应该采用哪种技术来保证数据的一致性？",
    "options": [
      "使用复合索引（Composite Index）",
      "请求负载均衡（Request Load Balancing）",
      "分布式事务（如 TCC、SAGA）",
      "滚动升级（Rolling Upgrade）"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档明确指出，当事务涉及多个分片时，单机事务已无法满足要求。此时需要引入分布式事务管理方案（如XA、TCC、SAGA）来协调多个分片的操作，确保它们要么全部成功，要么全部失败，从而保证数据的一致性。",
    "source": "文档中「2. 分片后的数据一致性」-「事务管理」部分",
    "hint": "当一个事务跨越了多个独立的数据库实例时，我们需要一种特殊的机制来协调它们。"
  },
  {
    "question": "如果一个平台希望按照 '华东区'、'华北区'、'华南区' 等具体的地理区域来划分用户数据，哪种分片规则最为合适？",
    "options": [
      "哈希分片 (Hash Sharding)",
      "范围分片 (Range Sharding)",
      "列表分片 (List Sharding)",
      "随机分片 (Random Sharding)"
    ],
    "correctAnswerIndex": 2,
    "explanation": "列表分片是根据预定义的分片列表进行数据划分的。这种方式非常适合按地区、部门等离散且固定的枚举值进行分片的场景。哈希分片更侧重于数据的均匀分布，而范围分片则适用于按连续的区间（如时间、ID范围）划分。",
    "source": "文档中「1. 分片策略选择」-「分片规则」部分",
    "hint": "哪种分片规则允许你根据一个预先定义好的、离散的集合（如城市列表）来存放数据？"
  },
  {
    "question": "在已经分片的系统中，处理跨分片查询（Cross-shard Query）的最佳实践是什么？",
    "options": [
      "尽可能在设计上避免跨分片查询",
      "将所有数据聚合到一个临时表中再进行查询",
      "禁止所有可能导致跨分片查询的业务功能",
      "为每个分片的数据实时同步到一个全局索引库"
    ],
    "correctAnswerIndex": 0,
    "explanation": "文档指出，应当“尽量避免跨分片查询”。这是因为跨分片查询需要聚合多个数据源的结果，通常性能较差且实现复杂。一个优秀的数据库分片设计，其标志就是绝大多数的查询都能在单个分片内完成。",
    "source": "文档中「3. 查询和索引设计」-「查询优化」部分",
    "hint": "跨分片查询会带来显著的性能和复杂性问题，因此在架构设计阶段应该采取什么策略来应对它？"
  },
  {
    "question": "为了在不中断整体服务的情况下对分片系统进行应用或数据库升级，文档推荐采用哪种策略？",
    "options": [
      "在业务低峰期一次性完成所有分片的升级",
      "先备份所有数据，然后停机升级",
      "采用滚动升级策略，逐个或分批升级分片",
      "只升级主分片，其他分片保持旧版本"
    ],
    "correctAnswerIndex": 2,
    "explanation": "滚动升级策略允许系统逐个或分批地升级节点（分片），在升级一部分节点的同时，其余节点仍然可以对外提供服务。这种方式可以避免全局停机，保证了系统在升级过程中的高可用性。",
    "source": "文档中「4. 数据迁移和升级」-「系统升级」部分",
    "hint": "想象一下如何像“滚动”的车轮一样，一部分一部分地完成升级，从而不让整个系统“停转”？"
  },
  {
    "question": "为什么在选择分片键时，确保其能“均匀分布数据”至关重要？",
    "options": [
      "为了方便进行数据加密",
      "为了避免某些分片过载而其他分片空闲（数据热点问题）",
      "为了简化备份和恢复的流程",
      "为了让所有分片的数据量完全一致"
    ],
    "correctAnswerIndex": 1,
    "explanation": "分片键若不能均匀分布数据，会导致数据和访问压力集中在少数分片上，形成“数据热点”或“负载热点”。这会使得这些过载的分片成为系统瓶颈，而其他分片资源闲置，违背了水平切分以分散压力、提升整体性能的初衷。",
    "source": "文档中「1. 分片策略选择」-「分片键选择」及「5. 负载均衡」-「分片负载均衡」部分",
    "hint": "如果数据分布不均，某些分片会变得比其他分片“热”得多，这会对系统的负载均衡带来什么问题？"
  },
  {
    "question": "文档中提到了“最终一致性”策略，它适用于以下哪种场景？",
    "options": [
      "处理银行转账等要求实时精确的金融交易",
      "用户登录时的密码验证",
      "对一致性要求不高的场景，例如社交媒体的点赞数统计",
      "数据库全局唯一ID生成服务"
    ],
    "correctAnswerIndex": 2,
    "explanation": "最终一致性允许数据在短时间内存在不一致的状态，但保证在一段时间后最终会达到一致。它适用于那些可以容忍短暂延迟和数据不一致，但追求更高系统可用性和性能的场景，例如社交动态、商品评论等。对于需要强一致性的场景（如金融交易、账户验证），则不适用。",
    "source": "文档中「2. 分片后的数据一致性」-「事务管理」部分",
    "hint": "思考一下，哪种业务场景下，数据晚几秒钟甚至几分钟才同步过来也是可以接受的？"
  }
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                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  